MDB Attoneys disgusting harassment

Dear sir/madam

I am being harassed by some lady claiming to call from Munnik Basson Dagama Incorporated Attorneys (MBD Attorneys). I get calls from +27 (79) ***, a lady on the line insists that I should provide my personal details over the phone because of some legal case with MTN. When I ask her to read through her records for me to confirm if she is talking to the right person, she just hangs up. I also get early morning (8:00) calls from +27 ***** with the last two digits changing all the time. When I answer, there is no response and the call just hangs up. Can someone please deal with this unprofessionalism. I always make it a point that my accounts are in order including my MTN account.